Majorizing sequences for Newton's method under centred conditions for the derivative

We present semi-local and local convergence results for Newton's method in order to approximate a locally unique solution of a nonlinear equation in a Banach space setting. Our technique is more flexible than in earlier studies such that [J.A. Ezquerro, D. González, and M.A. Hernández, Majorizing sequences for Newton's method from initial value problems, J. Comput. Appl. Math. 236 (2012), pp. 2246–2258; J.A. Ezquerro, D. González, and M.A. Hernández, A general semi-local convergence result for Newton's method under centred conditions for the second derivative, ESAIM: Math. Model. Numer. Anal. 47 (2013), pp. 149–167]. The operator involved is twice Fréchet-differentiable. We also assume certain centred Lipschitz-type conditions for the derivative which are more precise than the Lipschitz conditions used in earlier works. Numerical examples are used to show that our results apply to solve equations but earlier ones do not in the semi-local case. In the local case we obtain a larger convergence ball. These advantages are obtained under the same computational cost as before [17 J.A. Ezquerro, D. González, and M.A. Hernández, Majorizing sequences for Newton's method from initial value problems, J. Comput. Appl. Math. 236 (2012), pp. 2246–2258. doi: 10.1016/j.cam.2011.11.012[Crossref], [Web of Science ®] , [Google Scholar],18 J.A. Ezquerro, D. González, and M.A. Hernández, A general semilocal convergence result for Newton's method under centered conditions for the second derivative, ESAIM: Math. Model. Numer. Anal. 47 (2013), pp. 149–167. doi: 10.1051/m2an/2012026[Crossref], [Web of Science ®] , [Google Scholar]].     

Extending Query-Subquery Nets for Deductive Databases under the Well-Founded Semantics

ABSTRACT

We propose a method, called QSQN-WF, for evaluating queries to Datalog^¬ databases under the well-founded semantics. It is the first one that is set-at-a-time and strictly goal-directed w.r.t. SLS-resolution defined by Przymusinski. These properties are important for reducing accesses to the secondary storage and redundant computations. The first property distinguishes our method from the one based on SLG-resolution by Chen, Swift, and Warren (1995 Chen, W., T. Swift, and D. S. Warren. 1995. Efficient top-down computation of queries under the well-founded semantics. Journal of Logic Programming 24 (3):161–99. doi:10.1016/0743-1066(94)00028-5[Crossref] , [Google Scholar]) (which is tuple-at-a-time). The second property distinguishes our method from the ones based on the magic-sets transformation by Kemp, Srivastava, and Stuckey (1995 Kemp, D. B., D. Srivastava, and P. J. Stuckey. 1995. Bottom-up evaluation and query optimization of well-founded models. Theoretical Computer Science 146 (1 & 2):145–84. doi:10.1016/0304-3975(94)00153-a[Crossref], [Web of Science ®] , [Google Scholar]) and Morishita (1996 Morishita, S. 1996. An extension of Van Gelder's alternating fixpoint to magic programs. Journal of Computer and System Sciences 52 (3):506–21. doi:10.1006/jcss.1996.0038[Crossref], [Web of Science ®] , [Google Scholar]), which use magic atoms not in the most appropriate way and are not strictly goal-directed w.r.t. SLS-resolution. Our method follows SLS-resolution, with Van Gelder’s alternating fixpoint semantics on the background, but uses a query-subquery net to implement tabulation and the set-at-a-time technique, reduce redundant computations, and allow any control strategy within each iteration of the main loop. It is sound and complete w.r.t. the well-founded semantics and has PTIME data complexity.     

Perceptual and physiological heat strain: Examination in firefighters in laboratory- and field-based studies

Firefighting demands performing heavy muscular work under adverse and potentially dangerous conditions. Although the physiological and psychological responses to simulated firefighting activities have been described, the heat strain has not been characterised using standardised indices of exercise–heat strain. The purpose of the study is to describe the physiological and perceptual strain associated with working in personal protective equipment and performing simulated firefighting activities in a hot environment using recently developed strain indices (Physiological Strain Index (PhSI); Perceptual Strain Index (PeSI)). Data from two previously published studies (Smith et al. 1995 Smith, D. L. 1995. Selected physiological and psychological responses to physical activity in different configurations of firefighting gear. Ergonomics, 38: 2065–2077. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar], 2001 Smith, D. L. 2001. Effect of strenuous live-fire fire fighting drills on hematological, blood chemistry and psychological measures. Journal of Thermal Biology, 26: 375–379. [Crossref], [Web of Science ®] , [Google Scholar]) – one a laboratory-based study and one a field-based study – were re-analysed incorporating the strain indices. The laboratory study involved walking on a treadmill for 15 min while wearing three different clothing and equipment configurations. The field study involved three trials of standardised firefighting tasks in a live-fire training structure (mean trial length = 5.76 min). Heart rate, rectal temperature, thermal sensations and ratings of perceived exertion were collected in each study. PhSI and PeSI values were calculated using the formulae developed by Moran et al. (1998b Moran, D. S., Shitzer, A. and Pandolf, K. B. 1998b. A physiological strain index to evaluate heat stress. American Journal of Physiology, 275: R129–R134. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) and Tikuisis et al. (2002 Tikuisis, P., McLellan, T. M. and Selkirk, G. 2002. Perceptual versus physiological heat strain during exercise-heat stress. Medicine & Science in Sports & Exercise, 34: 1454–1461. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]), respectively. PhSI and PeSI increased significantly over time in both studies. Even relatively brief bouts of exercise while wearing heavy impermeable clothing or simulated firefighting activity in the heat results in moderate to high levels of heat strain as assessed by PhSI and PeSI.     

Are mobile phone conversations always so annoying? The ‘need-to-listen’ effect re-visited

According to Monk et al. (2004a Monk, A.F., et al., 2004a. Why are mobile phones annoying? Behaviour & Information Technology, 23 (1), 33–42. doi: 10.1080/01449290310001638496[Taylor & Francis Online], [Web of Science ®] , [Google Scholar]. Why are mobile phones annoying? Behaviour and Information Technology, 23 (1), 33–42), mobile phone conversations are annoying to overhear due to an involuntary need-to-listen in order to predict the inaudible half of the conversation. However, previous support for this need-to-listen explanation of annoyance has failed to consider the confound that mobile phone conversations also have less predictable acoustic patterns and has only investigated ‘neutral’ conversations. By staging mobile and face-to-face conversations in public, this study further supports the need-to-listen explanation. By removing the need-to-listen to the content of a mobile conversation through introducing foreign speech, bystanders no longer perceived the conversation as more annoying than a conversation between two co-present individuals, supporting the need-to-listen explanation over unpredictable acoustics. In two further experiments manipulating conversational content (‘neutral’ vs. ‘intriguing’), findings suggest that the need-to-listen to mobile phone conversations is not inherently annoying; it can be annoying or possibly even ‘interesting’ depending on the conversational content.     

Mean-square stability and error analysis of implicit time-stepping schemes for linear parabolic SPDEs with multiplicative Wiener noise in the first derivative

In this article, we extend a Milstein finite difference scheme introduced in 8 Giles, M. B. and Reisinger, C. 2012. Stochastic finite differences and multilevel Monte Carlo for a class of SPDEs in finance. SIAM Financ. Math., 3(1): 572–592. (doi:10.1137/110841916)[Crossref] , [Google Scholar] for a certain linear stochastic partial differential equation (SPDE) to semi-implicit and fully implicit time-stepping as introduced by Szpruch 32 Szpruch, L. 2010. Numerical approximations of nonlinear stochastic systems PhD Thesis, University of Strathclyde [Google Scholar] for stochastic differential equations (SDEs). We combine standard finite difference Fourier analysis for partial differential equations with the linear stability analysis in 3 Buckwar, E. and Sickenberger, T. 2011. A comparative linear mean-square stability analysis of Maruyama- and Milstein-type methods. Math. Comput. Simulation, 81: 1110–1127. (doi:10.1016/j.matcom.2010.09.015)[Crossref], [Web of Science ®] , [Google Scholar] for SDEs to analyse the stability and accuracy. The results show that Crank–Nicolson time-stepping for the principal part of the drift with a partially implicit but negatively weighted double Itô integral gives unconditional stability over all parameter values and converges with the expected order in the mean-square sense. This opens up the possibility of local mesh refinement in the spatial domain, and we show experimentally that this can be beneficial in the presence of reduced regularity at boundaries.     

Evaluation of CMODIS-measured radiance by a hyperspectral model

A Chinese Moderate Resolution Imaging Spectrometer (CMODIS), an ocean colour sensor onboard the ‘Shenzhou-3’ spaceship, was launched on 25 March 2002. Because CMODIS was not equipped with any onboard calibration systems, there were major concerns about the accuracy of the CMODIS radiance measurements as well as the reliability of the data processing and oceanographic applications. To clarify these concerns, a hyperspectral satellite remote sensing radiance evaluation model (HRSREM) was developed, based on a radiative transfer model with consideration of multiple-scattering effects and atmospheric absorption. The model was used to compute the total radiance at the top of the atmosphere (TOA) to evaluate the CMODIS-derived radiance. The accuracy of the model was validated by Gordon's algorithms [Wang, M. and Gordon, H.R., 1994 Wang, M. and Gordon, H.R. 1994. A simple, moderately accurate, atmospheric correction algorithm for SeaWiFS. Remote Sensing of Environment, 50: 231–239. [Crossref], [Web of Science ®] , [Google Scholar], A simple, moderately accurate, atmospheric correction algorithm for SeaWiFS. Remote Sensing of Environment, 50, pp. 231–239] and Sea-viewing Wide Field-of-view Sensor (SeaWiFS) data. The results show that the average relative error in the atmospheric scattering radiance computed by the HRSREM is less than 1.5% and the average error in the HRSREM TOA radiance is about 3.0%. Therefore, the HRSREM can be used to evaluate the accuracy of CMODIS-measured radiance. The results show that CMODIS has relatively small errors at the visible bands but large errors at the near-infrared (NIR) bands with an average error of more than 100%. The laboratory calibration coefficients are not reliable and the CMODIS data were recalibrated by the HRSREM to recover the archive of CMODIS data.     

DYNAMIC FUZZY OWA MODEL FOR EVALUATING THE RISKS OF SOFTWARE DEVELOPMENT

How to get the relative weights in multiple criteria decision making (MCDM) problems is an important issue. In 1988, Yager proposed an ordered weighted averaging (OWA) aggregation method to find the related weights of many criteria. However, the previous aggregation operators (including OWA) and the aggregation situation are independent. For solving the problem, we propose a new aggregation situation and operator model—a dynamic fuzzy OWA model based on the evaluating situation. The OWA can modify associated weights dynamically based on the aggregation situation and work like a “magnifying lens” to enlarge and find the most important attribute dependent on the minimal information, or get equal attributes' weights based on maximal information. We also evaluate the risks of software development and compare the results with Chen's (2001 Chen , S. M. 2001 . Fuzzy group decision making for evaluating the rate of aggregative risk in software development . Fuzzy Sets and Systems , 118 : 75 – 88 .[Crossref], [Web of Science ®] , [Google Scholar]) and Lee's (1996 Lee , H. M. 1996 . Group decision making using fuzzy sets theory for evaluating the rate of aggregative risk in software development . Fuzzy Sets and Systems , 80 : 261 – 271 .[Crossref], [Web of Science ®] , [Google Scholar]) methods.     

The nature and components of perceived behavioural control as an element of theory of planned behaviour

Ajzen (1991 Ajzen, I., 1991. The theory of planned behaviour. Organizational Behaviour and Human Decision Processes, 50(2), 179–211. doi: 10.1016/0749-5978(91)90020-T[Crossref], [Web of Science ®] , [Google Scholar]. The theory of planned behaviour. Organizational Behaviour and Human Decision Processes, 50 (2), 179–211) suggested three constructs that determine the user's intention: attitude, subject norms and perceived behavioural control (PBC). Recently, some psychologists have argued that PBC is poorly understood. This study attempted to investigate the nature and components of PBC in research adapting theory of planned behaviour (TPB) to predict the intentions of bank customers with regard to adoption of Internet banking. The findings show some difficulty in discriminating between the presumed internal and external determinants of PBC. This study identifies two determinants: (1) self-efficacy (SE) and (2) facilitating conditions. The latter is broken into three facilitation factors: (1) resources, (2) technology and (3) government support (GS). Interestingly, SE, if considered as an internal factor, exhibits a significance effect on PBC in the presence of the three external factors. This shows that the external factors have a significance effect on PBC when entered for regression analysis without SE. These are valuable findings which show that both components of one's belief in one's level of control (internal factors: SE; external factors: resources, technology and GS) are important. However, which factors have the greatest effect on PBC might be related to the type of innovation or to other factors.     

Explaining Instant Messaging Continuance Intention: The Role of Personality

The Five-Factor Model (FFM) of personality is widely used to predict cognitions, attitudes, and behaviors in management and psychological research. However, the FFM personality has seldom appeared in the information system (IS) research field. Devaraj, Easley, and Crant (2008 Devaraj, S., Easley, R. F. and Crant, J. M. 2008. How does personality matter? Relating the five-factor model to technology acceptance and use. Information Systems Research, 19: 93–105. [Crossref], [Web of Science ®] , [Google Scholar]) first introduced FFM into the context of IS acceptance. This study extends to the context of IS continuance. The proposed model is developed and empirically validated using data from a field survey in order to examine how individuals' personality traits influence their IS continuance intentions. The data were collected from a public university in China via an online survey. The findings support that user satisfaction and perceived usefulness are key to continuance intention of instant messaging use. The results also support that perceived enjoyment and perceived usefulness are positively associated with user satisfaction. Perceived enjoyment is the dominant variable affecting user satisfaction with technology use. Two personality traits of the Big Five factors (i.e., Conscientiousness and Extraversion) have direct effects on perceived enjoyment, whereas the other three (i.e., Openness to Experience, Neuroticism, and Agreeableness) have no direct effects. Our study provides an important basis for better understanding how individuals' personality characteristics influence their technology continuance.     

An Experimental Analysis of Experiential and Cognitive Variables in Web Navigation

Cognitive and experiential factors in human–computer interaction have been the focus of significant recent attention, but there is a lack of a much needed integrated approach to these issues. The current article proposes such an approach and applies this, combined with the person–task–artifact model (Finneran & Zhang, 2003 Finneran, C. and Zhang, P. 2003. A Person-Artefact-Task (PAT) model of flow antecedents in computer-mediated environments. International Journal of Human–Computer Studies, 59: 475–496. [Crossref], [Web of Science ®] , [Google Scholar]), to the modeling of web navigation. In an experiment, artifact complexity and task complexity were manipulated. The effects of the experimental manipulations and intrinsic motivation on flow experience, task performance and task outcome were tested. The main effects of the manipulations were confirmed. Further analyses demonstrated that flow was a mediator of the effect of experimental manipulations on task performance, and task performance was a mediator of the effect of flow on task outcome. Overall, the results in the domain of web navigation that are presented here demonstrate the need for taking an integrated cognitive-experiential approach in the modeling of human–computer interaction.     

Perception and biomechanics data in a manual handling task: a comparative study

This paper explores the use of subjective perception tasks and its correlations with biomechanical data in the evaluation of manual material handling. Three main dimensions were considered for perception: physical regroups sensations issued from a specific body area; operative regroups feelings related to the execution of the task; and performance regroups feelings that involve a judgement on the execution or reflect overall sensations. The following questions were then explored. To what extent are perception data related to biomechanics data? Do both approaches lead to similar conclusions or interpretations when effect of practice, format and off-centre were tested? How can they complement one another? The task consisted of transferring 50 series of three 15 kg loads in order to verify the impact of free practice, format (box/cylinder) and load centre of gravity position. Eleven subjects rated perception on a CR-10 scale (Borg 1982 Borg, G. A.V. 1982. Psychophysical bases of perceived exertion. Medicine and Science in Sports and Exercise, 14: 377–381. [Crossref], [PubMed], [Web of Science ®] , [Google Scholar]) after each series. The session was completed with an interview on perception. The net resulting moment was systematically found to be the best correlated with data perception. While all physical and performance items corresponded in various ways to biomechanics data, perceptions associated with operative dimension appeared to be less related with biomechanical data. As regards the impact of practice, format and off-centre, both approaches would lead to the same conclusions, except for the effect of the off-centre. Verbal data add rational information about how or why perception can or cannot be reflected in biomechanics data. How both approaches can be matched more closely in manual handling is discussed.     

A FORMALISM FOR A CASE STUDY IN THE WATERTIME PROJECT: THE CITY WATER SYSTEM IN GRENOBLE,FROM PRIVATIZATION TO REMUNICIPALIZATION

The formal representation for legal or other narratives as introduced by Nissan (2001 Nissan, E. 2001. A formalism for competing claims of identification: The “Smemorato di Collegno” amnesia case. Informatics and Computing, 20(6): 625–656. [Web of Science ®] , [Google Scholar]; ; 2003a Nissan, E. 2003a. Identification and doing without it, I: A situational classification of misapplied personal identity, with a formalism for a case of multiple usurped identity in Marivaux. Cybernetics and Systems, 34(4–5): 317–358. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]; 2003b Nissan, E. 2003b. Identification and doing without it, II: Visual evidence for pinpointing identity. How Alexander was found out: Purposeful action, enlisting support, assumed identity, and recognition. A goal-driven formal analysis. Cybernetics and Systems, 34(4–5): 359–380. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]; 2003d Nissan, E. 2003c. Identification and doing without it, III: Authoritative opinions, purposeful action, relabelled goods, and forensic examinations. The case of the stuffed birds: Its narrative dynamics set in formulae. Cybernetics and Systems, 34(6–7): 467–500. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]; 2003a Nissan, E. 2003a. Identification and doing without it, I: A situational classification of misapplied personal identity, with a formalism for a case of multiple usurped identity in Marivaux. Cybernetics and Systems, 34(4–5): 317–358. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar] is adapted to the analysis of a case study in WaterTime, a project developed by David Hall and his collaborators in view of the development of a decision model for policy making, concerning the privatization of city water systems throughout the European Union. In WaterTime, the experience of several cities is analyzed and compared. In particular, have analyzed the privatization, in 1989, of the city water system in Grenoble, France. Eventually, corruption was proven, and the system was partly remunicipalized; court decisions led to its full remunicipalization. We sketch a symbolic representation of events in this narrative.     

Models of the effect of teleoperation transmission delay on robot movement time

Abstract

Recent research of [Scholcover and Gillan (2018 Scholcover, F., and D. J. Gillan. 2018. “Using Temporal Sensitivity to Predict Performance under Latency in Teleoperation.” Human Factors 60.1:80–91. doi:10.1177/0018720817734727.[Crossref], [Web of Science ®] , [Google Scholar])] has shown experimentally that system transmission delay has a linear effect on the time taken to perform a complex tracking task with a simple teleoperated robot. This note shows that, for the case of moving a robot through a straight path, this relationship is predicted. The result is a simple modification of Drury’s law to take into account the system delay. This work extends the model for performance under intermittent illumination of Drury to the effects of fixed delays in task performance, occurring with teleoperated robots. In all cases, there was empirical evidence for the predicted linear relationship.

Practitioner summary: When there is a delay in system response for robotic teleoperation between a control input and system output, movement time (MT) is increased and the increased times are linearly related to the system delay. This is true for zero and first-order control and for delays occurring before and after the control action.     

Knowledge processes in virtual teams: consolidating the evidence

This article takes stock of the current state of research on knowledge processes in virtual teams (VTs) and consolidates the extent research findings. Virtual teams, on the one hand, constitute important organisational entities that facilitate the integration of diverse and distributed knowledge resources. On the other hand, collaborating in a virtual environment creates particular challenges for the knowledge processes. The article seeks to consolidate the diverse evidence on knowledge processes in VTs with a specific focus on identifying the factors that influence the effectiveness of these knowledge processes. The article draws on the four basic knowledge processes outlined by Alavi and Leidner (2001 Alavi, M.Leidner, D.E., 2001. Review: knowledge management and knowledge management systems: conceptual foundations and research issues. MIS Quarterly, 25 (1), 107–136. doi: 10.2307/3250961[Crossref], [Web of Science ®] , [Google Scholar]) (i.e. creation, transferring, storage/retrieval and application) to frame the investigation and discuss the extent research. The consolidation of the existing research findings allows us to recognise the gaps in the understanding of knowledge processes in VTs and identify the important avenues for future research.     

Spatial pattern of a seismo-ionospheric signature using principal component analysis

This article uses principal component analysis (PCA) to determine the spatial pattern of total electron content (TEC) anomalies in the ionosphere corresponding to China's Wenchuan Earthquake of 12 May 2008 UTC (M_w?=?7.9). PCA is applied to global ionospheric maps (GIMs) with transforms conducted for the time period from 08:00 to 10:00 UT on 9 May 2008. The GIMs are subdivided into 100 smaller maps (36° longitude and 18° latitude). The smaller maps (71?×?71 pixels) form the transform matrices of corresponding dimensions (2?×?1) through image processing. The transform allows for extreme principal eigenvalues to be assigned to the seismo-ionospheric signature described by Zhao et al. [2008 Zhao, B., Yu, T., Wang, M., Wan, W., Lei, J., Liu, L. and Ning, B. 2008. Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake?. Journal of Geophysical Research, 113: A11304 doi:doi: 10.1029/2008JA013613[Crossref], [Web of Science ®] , [Google Scholar], Is an unusual large enhancement of ionospheric electron density linked with the 2008 great Wenchuan earthquake? Journal of Geophysical Research, 113, A11304, doi: 10.1029/2008JA013613.]. Results show that the range of the TEC anomaly declines with height; however, the anomaly becomes more localized and intense at higher altitudes (250–300 km), giving the anomaly the spatial pattern of a downward-facing trumpet.     

Development of an Instrument to Measure Enjoyment of Computer Game Play

This article reports on the development of an instrument designed to measure the enjoyment of computer game play. Despite the enormous technological progress in the field of computer games, enjoyment of computer game play is still not a well-defined construct. Based on Nabi and Krcmar's (2004 Nabi, R. L. and Krcmar, M. 2004. Conceptualizing media enjoyment as attitude: Implications for mass media effects research. Communication Theory, 14: 288–310. [Crossref], [Web of Science ®] , [Google Scholar]) tripartite model of media enjoyment, a survey questionnaire was developed to measure computer game players' affective, behavioral, and cognitive reactions. Expert consultation, exploratory, and confirmatory card sorting sessions were used to refine the instrument. A survey of computer game players was subsequently conducted to test the instrument. Reliabilities and construct validities were analyzed. Findings and their implications were discussed.     

Chlorophyll concentration mapping with MIVIS data to assess crown discoloration in the Ticino Park oak forest

Airborne hyperspectral remote observations, characterized by high spatial and spectral resolution, allow the estimation of quantitative vegetation variables useful in forest condition assessment. In this research, total chlorophyll (a?+ b) concentration (C _ab), a biochemical variable describing crown discoloration rate, was mapped to assess oak (Quercus robur L.) condition in the Ticino Regional Park. A simulation experiment was conducted to evaluate the error in C _ab estimation due to ecological variables (i.e. canopy leaf area index and understorey characteristics) and to sun-sensor configurations when optical indices are used. Canopy reflectance was simulated by means of the PROSPECT leaf radiative transfer model (Jacquemoud and Baret 1990 Jacquemoud, S. and Baret, F. 1990. PROSPECT: a model of leaf optical-properties spectra. Remote Sensing of Environment, 34: 75–91. [Crossref], [Web of Science ®] , [Google Scholar]) coupled with the SAILH canopy radiative transfer model, a variation of the SAIL (Scattering by Arbitrarily Inclined Leaves) model modified to include the hot spot effect (Verhoef 1984 Verhoef, W. 1984. Light scattering by leaf layers with application to canopy reflectance modeling: The SAIL model. Remote Sensing of Environment, 16: 125–141. [Crossref], [Web of Science ®] , [Google Scholar], Kuusk 1991 Kuusk, A. 1991. “The hot-spot effect in plant canopy reflectance”. In Photon–Vegetation Interactions: Application in Optical Remote Sensing and Plant Ecology, Edited by: Mynemi, R. and Ross, J. 139–159. New York: Springer Verlag. [Crossref] , [Google Scholar]). The vegetation was modelled as a two layer medium with oak canopy as the top layer and the understorey as the bottom layer. Simulations were performed for varying leaf C _ab and canopy Leaf Area Index (LAI) of the top layer, θ_l (mean leaf inclination angle) and LAI of the bottom layer (LAI_u) and sun-sensor geometry. Optical indices were calculated and used in C _ab retrieval. Simulations demonstrated that errors in C _ab estimation were negligible when MTCI (MERIS Terrestrial Chlorophyll Index) was used, thus indicating that MTCI was the most reliable index in mapping C _ab in this forest environment. Empirical models based on optical indices were developed to map C _ab from Multispectral Infrared and Visible Imaging Spectrometer (MIVIS) images acquired by an airborne survey on the Park forested area. A regression analysis between C _ab concentration measured in leaves sampled in field and optical indices computed from hyperspectral MIVIS data was conducted. The MTCI index showed the highest performances and was therefore used to map C _ab concentration of the Ticino Park oak forest. The C _ab map was then used to assess crown discoloration level.     

MBNS Steganogram Detection and Payload Capacity Estimation Exploiting the Statistical Moments of Entropy Measure

ABSTRACT

Multiple Base Notational System (MBNS) steganography (Zhang & Wang, 2005 Zhang, X. and Wang, S. 2005. Steganography using multiple-base notational system and human vision sensitivity. IEEE Signal Processing Letters, 12(1): 67–70. [Crossref], [Web of Science ®] , [Google Scholar]) scheme employs human vision sensitivity to hide a large amount of secret bits into a still image with a high imperceptibility and is demonstrated to be robust to statistical analysis. In MBNS steganography, secret data are converted into symbols in a notational system with multiple bases. The pixels of a host image are then altered such that their remainders are equal to the symbols, when the pixel values are divided by the bases. Empirically it is observed that the moments of the entropy measure of the remainders in a stego image are larger than that of its clean counterpart. Based on this observation, we propose an active steganalytic approach which effectively breaks the MBNS steganography even with 5% payload capacity, utilizing these moments as features and also makes an estimation of the embedding rate. Experimental results demonstrate that the proposed scheme significantly outperforms prior arts in classification accuracy.     

An open book on Facebook? Examining the interdependence of adolescents’ privacy regulation strategies

Users of social network sites (SNSs) use three main strategies that help to manage the privacy of their profile information: (1) limiting the level of data revealed, (2) using privacy settings to exert control over data and (3) audience/friendship management by being restrictive about whom to accept as a ‘friend’. Extant research does not show whether these strategies operate as independent mechanisms or whether they are interdependent and work as a system. Given what offline privacy theorist Irwin Altman (1977 Altman, Irwin. 1977. “Privacy Regulation: Culturally Universal or Culturally Specific?” Journal of Social Issues 33 (3): 66–84. doi: 10.1111/j.1540-4560.1977.tb01883.x[Crossref], [Web of Science ®] , [Google Scholar]) designates as the multi-mechanic nature of privacy protection, we test a model in which we expect to find that the three discerned strategies are related to one another. Structural equation modelling analysis performed on the subsample (n?=?1564) of our study’s data – collected among 1743 adolescents by means of a paper-and-pencil survey – demonstrates that, in line with Altman’s vision of privacy protection, the three discerned strategies effectively operate as an interdependent system. In congruence with the hypotheses derived from extant research, we found that adolescents’ level of disclosure influences adolescents’ involvement in the two other discerned strategies: Adolescents with high levels of personal information disclosure share an increased tendency to have many friends on SNSs and a lower level of using privacy settings.     

Underwater movement times with ongoing visual control

Arm movements made in a water environment take longer to perform than in an air environment due to the drag forces experienced by the arm. Movement times for ballistic underwater movements have been accurately modelled by Hoffmann and Gan (1988 Hoffmann, E.R. and Gan, K-C. 1988. Underwater ballistic movements. Ergonomics, 31(9): 1305–1316. [Taylor & Francis Online], [Web of Science ®] , [Google Scholar]). The present work models the movement time for movements that require ongoing visual control. In these movements, the ‘distance-covering’ phase is carried out at high speeds and will be affected by the fluid characteristics, while the ‘homing-in’ phase, where speeds are low, is less affected. An experiment is reported that models these effects and which indicates that a ballistic component needs to be added to the standard Fitts model in order to account for the drag forces in the distance-covering phase of the movement.

Practitioner Summary: Many tasks, such as maintenance and salvage work, require work to be done underwater. Times for performing underwater tasks are generally longer than on land. This article is one step in modelling the difference in task times for land and underwater movements.